<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
<style>
    .ck:checked{
        width: 20px;
        height: 20px;
    }
</style>
</head>

<body>
    <input type="checkbox" class="ck">
    <input type="checkbox" class="ck">
    <input type="checkbox" class="ck">
    <input type="checkbox" class="ck">
</body>
</html>